Compounds and methods for reducing undesired toxicity of chemotherapeutic agents

ABSTRACT

Novel compositions and formulations are disclosed that have use as toxicity-reducing agents for various chemotherapeutic agents and as treatment for certain diseases and conditions. The compositions of matter are amino acid and peptide heteroconjugated disulfides of 2-mercaptoethane sulfonate sodium.

RELATED APPLICATIONS

The present patent application is a Divisional Application of U.S.patent application Ser. No. 10/843,930, filed on May 12, 2004 andentitled “COMPOUNDS AND METHODS FOR REDUCING UNDESIRED TOXICITY OFCHEMOTHERAPEUTIC AGENTS”.

FIELD OF THE INVENTION

The present invention relates to novel compositions of matter, namelycertain short-chain peptides, and short chain peptides conjugated with athioalkane sulfonate or phosphonate salt. The compositions, whenadministered to patients also receiving chemotherapy for cancer or otherdiseases, are useful as protective agents to mitigate or eliminate theundesired toxic effects of the chemotherapeutic agent.

BACKGROUND OF THE INVENTION

Since the discovery of the antineoplastic properties of the nitrogenmustards more than 50 years ago, cancer chemotherapy has been anexpanding area of scientific endeavor, and has been a critical componentof cancer treatment along with surgery and radiation therapy. Wherechemotherapy was once accepted only as a means to extend survival timefor those patients diagnosed as incurable by surgery and/or radiationtherapy, it is now a recognized modality of treatment in nearly all ofthe more than two thousand variations of cancer.

Modern cancer chemotherapy typically involves a combination of two orthree different drugs, and the advances in technology and medicalknowledge have greatly improved a patient's chances of recovery in manyforms of cancer. The role of antineoplastic agents in cancer therapyvaries widely depending upon the form of cancer. For example,chemotherapy is often the primary course of therapy in cancers of theovary, testis, breast, bladder, and others, in leukemias and lymphomas,and is generally employed in combination with radiation therapy in thetreatment of a large number of sarcomas, melanomas, myelomas, andothers. In contrast, chemotherapy is often used only as a last resort oras a palliative treatment for most solid tumors, such as carcinomas ofthe pancreas and lung. There are exceptions within each class of tumoror other neoplasm.

Chemotherapeutic agents, which are commonly referred to throughout thisspecification as “antineoplastic agents” are classified into a number ofdiverse groups. The vast majority of these agents act as cytotoxicdrugs, and each member of a specific group is postulated to typicallyexert its cytotoxic effects through a similar biological mechanism.However, it is important to note that a complete understanding of thebiological and biochemical mechanisms of action of antineoplastic drugsis not fully known. The mechanisms of action recited in thisspecification are based upon the current state of the art, and each ofthese postulated mechanisms may or may not be important to the mechanismof actual cytotoxicity of the drug, or the manner in which theprotective agents allay the toxic incidences recited herein.

Unfortunately, nearly all of the antineoplastic agents in use today havethe potential to produce significant toxic effects on normal healthycells apart from the desired killing effects on cancer cells. Drugtoxicity can be severe enough to create life-threatening situations,which requires the coadministration of other drugs, the reduction and/ordiscontinuation of the antineoplastic drug, or the performance of otherprophylactic maneuvers, any of which may impact negatively on thepatient's treatment and/or the quality of life. Many times, the failureto achieve control of a patient's disease is due to the measures thatmust be taken to reduce the unwanted toxicity of the antineoplasticagent on healthy cells.

As of January 2003, more than eighty commercial antineoplastic agentshave been approved for use in the United States. Even moreantineoplastic agents are approved for usage overseas. There are alsoover two hundred investigational new drugs which are undergoingevaluation as antineoplastic agents in clinical trials in the UnitedStates and overseas. In addition, thousands of newly discoveredcompounds are evaluated every year as potential antineoplastic agents.

Mesna (Sodium 2-mercaptoethane sulfonate; Mesnex®) is an internationallyapproved drug for use in conjunction with ifosfamide, to reduce thebladder toxicity commonly associated with therewith. The mechanism ofaction of mesna has been postulated to be its ability to react withacrolein, a metabolite of ifosfamide. Previous teachings taught thatmesna was auto-oxidized in the mildly basic environment of blood plasma,and was reduced back to mesna in the acidic environment present in thekidneys and bladder.

Our investigations into the pharmacokinetics of mesna suggest that, inthe human bloodstream, mesna reacts with various mercapto-containingamino acids, such as cysteine, homocysteine and glutathione to formdisulfides of a heteroconjugate variety. Previously, disulfides ofmesna, both the homoconjugate and the disulfide heteroconjugates werethought to be inactive, and that reduction to mesna was required for thedrug to work.

Contrary to the prior teachings that suggested its inactive nature,BNP7787 (Disodium 2,2′-dithiobis ethane sulfonate; Tavocept™), thehomoconjugated disulfide of mesna, is currently in late-stage humanclinical trials in the United States, Europe and Japan as atoxicity-reducing agent when used in conjunction with cisplatin,carboplatin, paclitaxel, and combination regimens thereof. BNP7787 hasalso been disclosed in a number of United States and internationalpatents as an effective toxicity-reducing agent for a number of otherchemotherapeutic drugs.

SUMMARY OF THE INVENTION

The present invention discloses compounds that are heteroconjugates ofmesna, which are useful as toxicity-reducing agents when used incombination with various chemotherapeutic agents. The compounds possessthe following Formula I: (I) X—S—S—R₁—R₂, wherein:

-   -   R₁ is lower alkylene, optionally substituted by aryl, hydroxy,        alkoxy, aryloxy, mercapto, alkylthio or arylthio for a        corresponding hydrogen atom;    -   R₂ is sulfonate or phosphonate;    -   X is a sulfur-containing amino acid or a peptide consisting of        2-10 amino acids, optionally substituted by lower alkyl, lower        alkenyl, lower alkynyl, aryl, alkoxy, aryloxy, mercapto,        alkylthio or hydroxy for a corresponding hydrogen atom; and    -   pharmaceutically acceptable salts and prodrugs thereof.

The present invention also provides for pharmaceutical formulationscontaining a Formula I compound as the active agent, combined with oneor more pharmaceutically acceptable excipients, fillers, diluents oradditives to form a pharmaceutically elegant formulation suitable foradministration to human patients.

The present invention also provides for methods of reducing the toxicityof treatment regimens that include administration of one or morechemotherapeutic agents. The methods of use involve administering aneffective, or toxicity-reducing amount of Formula I compound to apatient undergoing chemotherapy for cancer or other disease.

It is a principle object of the present to provide for novel and usefulcompounds that reduce or eliminate the undesirable toxicities associatedwith chemotherapy treatments.

Another object is to provide for pharmaceutical formulations of thenovel compounds that may be administered safely and efficiently.

Yet another object is to provide methods for reducing or eliminating theundesirable toxicities commonly associated with chemotherapy.

Various additional objects will become apparent upon a reading of thefollowing description and claims.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1: Scheme 1 illustrates a preferred synthesis of the resin-boundmesna intermediates. The resin, preferably polystyrene microspheres of200-400 mesh size, is functionalized with an appropriate linker, shownin Scheme 1 as sodium sulfinate.

FIG. 2: Scheme 2 illustrates the synthesis of the Formula I compounds ofthis invention where R₁ is ethyl and R₂ is sulfonate. As shown, thesynthetic process is a one-step, single pot process in which the polymerbound mesna is reacted with a sulfur-containing amino acid, preferablycysteine, homocysteine or glutathione; or by a short-chain peptidehaving 2-10 amino acids, at least one of which is a sulfur-containingamino acid.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments herein described are not intended to beexhaustive or to limit the invention to the precise form disclosed. Theyare chosen and described to explain the principles of the invention, andits application and practical use to thereby enable others skilled inthe art to follow its teachings.

DEFINITIONS

“Lower alkylene” means a bridging moiety formed of one to six ‘—CH₂—’groups.

“Aryl” means an aromatic ring or ring system consisting of one or morerings, preferably one to three rings, fused or unfused, with the ringatoms consisting entirely of carbon atoms.

“Lower alkyl” means a straight or branched-chain aliphatic hydrocarboncontaining one to six carbon atoms.

“Lower alkenyl” and “lower alkynyl” means a straight or branched chainhydrocarbon containing one to six carbon atoms, and with at least onedouble bond (alkenyl) or triple bond (alkynyl) between two of the carbonatoms.

The present invention comprises novel compounds having the formula: (I)X—S—S—R₁—R₂, wherein:

-   -   R₁ is lower alkylene, optionally substituted by aryl, hydroxy,        alkoxy, aryloxy, mercapto, alkylthio or arylthio for a        corresponding hydrogen atom;    -   R₂ is sulfonate or phosphonate;    -   X is a sulfur-containing amino acid or a peptide consisting of        2-10 amino acids, optionally substituted by lower alkyl, lower        alkenyl, lower alkynyl, aryl, alkoxy, aryloxy, mercapto,        alkylthio or hydroxy for a corresponding hydrogen atom; and    -   pharmaceutically acceptable salts and prodrugs thereof.

The present invention also comprises pharmaceutical formulations thatinclude a Formula I compound as active ingredient, and one or morepharmaceutically acceptable excipients, diluents, additives, fillers,etc., wherein the formulation is adapted for administration to mammalianpatients.

The present invention also includes methods of reducing the toxicity ofvarious antineoplastic and other drugs by administering effectiveamounts of the Formula I compound (or a formulation thereof) to thepatient in conjunction with the antineoplastic drug.

The Formula I compounds are heteroconjugated disulfides of mesna(2-mercaptoethane sulfonate sodium). The preferred method ofsynthesizing a Formula I compound is shown in FIG. 1 (Scheme 1) and FIG.2 (Scheme 2).

Scheme 1 in FIG. 1, illustrates a preferred synthesis of the resin-boundmesna intermediates. The resin, preferably polystyrene microspheres of200-400 mesh size, is functionalized with an appropriate linker, shownin Scheme 1 as sodium sulfinate. The functionalization of the resin ispreferably carried out in a two-step process as shown. First, the resinis combined with a halogenated reactant to form an intermediate sulfinylchloride linked resin, then a substitution reaction forms thesulfinate-linked resin.

2-mercaptoethane sulfonate sodium is then functionalized with anappropriate leaving group, preferably a nitric oxide moiety, and thenreacted with the functionalized polystyrene to form the intermediatepolymer bound mesna.

Scheme 2 in FIG. 2, illustrates the synthesis of the Formula I compoundsof this invention where R₁ is ethyl and R₂ is sulfonate. As shown, thesynthetic process is a one-step, single pot process in which the polymerbound mesna is reacted with a sulfur-containing amino acid, preferablycysteine, homocysteine or glutathione; or by a short-chain peptidehaving 2-10 amino acids, at least one of which is a sulfur-containingamino acid. Configuration of the reactant amino acid(s) may be pureL-enantiomer, pure D-enantiomer, or a racemic mixture of the D and Lstereoisomers.

After separation of the resin by conventional methods, virtually pureFormula I compound is obtained in high yields. The polymer boundsulfinate can be used again in the same or similar reactions.

Preferred compounds of Formula I include those compounds where X isselected from the group consisting of: cysteine (cys); homocysteine(h-cys); glutathione (GSH); glutamic acid (glu); and short-chainpeptides including cyteinyl glycine (cys-gly); glycinyl cysteine(gly-cys); glu-cys; cys-glu; glu-gly; and gly-glu. As stated above, theoptical configuration of the amino acids can be the levorotatory (L)configuration, the dextrorotatory (D) configuration, or a racemicmixture thereof. Most preferred is the more active, naturally-occurringL-isomer in each case. Detailed examples of the synthesis of certainFormula I compounds are set forth below.

The invention also includes pharmaceutical formulations that comprise aFormula I compound and one or more pharmaceutically acceptable solvents,excipients, diluents, fillers or additives, to construct apharmaceutically elegant formulation suitable for administration tomammalian patients.

The compounds of the present invention are preferably formulated priorto administration. Therefore, another aspect of the present invention isa pharmaceutical formulation comprising a compound of Formula I and apharmaceutically acceptable carrier, diluent, or excipient. The presentpharmaceutical formulations are prepared by known procedures usingwell-known and readily available ingredients. In making the compositionsof the present invention, the active ingredient will usually be mixedwith a carrier; or dissolved or suspended in a solvent; or enclosedwithin a carrier, which may be in the form of a capsule, sachet, paper,or other container. The compositions can be in the form of tablets,pills, powders, lozenges, sachets, cachets, elixirs, suspensions,emulsions, solutions, syrups, aerosols, ointments containing, forexample up to 10% by weight of active compound, soft and hard gelatincapsules, suppositories, sterile injectable solutions, and sterilepackaged powders.

Some examples of suitable carriers, excipients, and diluents includelactose, dextrose, sucrose, sorbitol, mannitol, starches, gum, acacia,calcium phosphate, alginates, tragacanth, gelatin, calcium silicate,microcrystalline cellulose, polyvinylpyrrolidone (PVP),dimethylacetamide (DMA), dimethylisosorbide (DMI), N-methylpyrrolidinone(NMP), cellulose, water syrup, methyl cellulose, methyl and propylhydroxybenzoates, talc, magnesium stearate and mineral oil. Theformulations can additionally include lubricating agents, wettingagents, emulsifying and suspending agents, preserving agents, sweeteningagents, or flavoring agents. Compositions of the inventions may beformulated so as to provide quick, sustained, or delayed release of theactive ingredient after administration to the patient by employingprocedures well known in the art.

The compositions are preferably formulated in a unit dosage form, eachdosage containing from about 5 mg to about 50,000 mg, more preferablyabout 25 to about 30,000 mg of the active ingredient. The most preferredunit dosage form contains about 10,000 mg of the active ingredient. Theterm “unit dosage form” refers to a physically discrete unit suitable asunitary dosages for human subjects and other mammals, each unitcontaining a predetermined quantity of active material calculated toproduce the desired therapeutic effect, in association with a suitablepharmaceutical carrier. The following formulation examples areillustrative only and are not intended to limit the scope of theinvention in any way.

Formulation 1

Hard gelatin capsules are prepared using the following ingredients:

Ingredient Amount Active Ingredient 1000 mg Dried Starch  800 mgMagnesium Stearate  20 mg

Formulation 2

A tablet is prepared using the following ingredients:

Ingredient Amount Active Ingredient 1000 mg Microcrystalline Cellulose 600 mg Silicon Dioxide, Fumed  10 mg Stearic Acid  10 mgThe components are blended and compressed to form tablets.

Formulation 3

Tablets each containing Formula I compound as an active ingredient aremade as follows:

Ingredient Amount Active Ingredient 1000 mg  Starch 600 mgMicrocrystalline Cellulose 300 mg PVP  2 mg Magnesium Stearate  2 mg

The active ingredient, starch and cellulose are passed through a No. 45mesh U.S. sieve and mixed thoroughly. The solution of PVP is mixed withthe resultant powders, which are then passed through a No. 14 mesh U.S.sieve. The granules so produced are dried at 50° C. and passed through aNo. 18 mesh U.S. sieve. The sodium carboxymethyl starch, magnesiumstearate and talc, previously passed through a No. 60 mesh U.S. sieve,are then added to the granules which, after mixing, are compressedutilizing a tablet machine to yield tablets each weighing approximately2 g.

Formulation 4

Suspensions each containing 4,000 mg of medicament per 80 mL dose aremade as follows:

Ingredient Amount Active Ingredient 4,000 mg Distilled Water 80 mL Syrup3 mL Benzoic Acid Solution 1.0 mL Artificial Flavor q.v. ArtificialColor q.v. Sodium Carboxymethyl Cellulose 400 mg

The medicament is passed through a No. 45 mesh U.S. sieve and mixed withthe sodium carboxymethyl cellulose and syrup to form a smooth paste. Thebenzoic acid solution, flavor and color are diluted with some of thewater and added, with stirring. Sufficient water is then added toproduce the required volume.

Formulation 5

An intravenous formulation may be prepared as follows:

Ingredient Amount Active Ingredient 10 g Purified Water 250 mL Mannitol100 mg 1 N Sodium Hydroxide 1 mL

The following examples illustrate one preferred synthesis of some of theFormula I compounds. These examples are disclosed for illustrativepurposes only, and are not to be construed as limiting the scope of theinvention in any way.

Example 1 Preparation of Resin Bound Mesna Intermediate from Sodium2-Mercaptoethane Sulfonate

A mixture of polystyrene resin (5.0 g, Fluka, 200-400 mesh; 1%divinylbenzene) and chlorosulfonic acid (100 g) in 300 mLdichloromethane was stirred at room temperature under argon forapproximately four hours, and then heated to reflux overnight. The resinwas isolated by filtration while the reaction was allowed to cool toroom temperature. Once the reaction temperature had cooled to roomtemperature, it was washed with dichloromethane (100 mL), acetonitrile(100 mL), and cold water (200 mL) sequentially. The pale brown-coloredresin was then dried under high vacuum to give 9.04 g poly(styrenep-sulfonyl chloride) with 93% yield.

Poly(styrene p-sulfonyl chloride) resin (9.04 g) was suspended in 200 mLaqueous solution of sodium sulfite (60 g) and stirred at 60° C. forapproximately 24 hours, isolated by filtration, washed with 200 mLwater, and dried to give 8.4 gram product of mono sodium, polystyrenep-sulfinate with 99% yield.

To a solution of hydrochloric acid (2 N, 40 mL) bubbled with argon wasadded sodium 2-mercaptoethane sulfonate (6.56 g). The reaction solutionwas cooled to 0° C. in an ice bath. 20 mL aqueous solution of sodiumnitrite (2.76 g) was added slowly. The reaction solution turned red andwas stirred for approximately 40 minutes after the addition. The monosodium, polystyrene p-sulfinate (3.8 g) was added and the mixture wasstirred at room temperature for approximately 16 hours. The resultingpolystyrene p-sulfinate bound 2-mercaptoethane sulfonic acid sodium saltwas isolated by filtration, rinsed with water and dried to give 3.9 g ofthe title intermediate.

Example 2 L-Cysteine-Mesna Disulfide

L-Cysteine (0.50 g, 4.1 mmol) was dissolved in 50 mL de-ionized waterbubbled with argon. Excessive polystyrene p-sulfinate bound2-mercaptoethane sulfonic acid sodium salt (about 17 fold) was added.The reaction mixture was stirred under argon for approximately 4 daysuntil all starting material of L-cysteine was consumed. The resin wasremoved by filtration and was recycled to prepare more disulfides. ThepH of the filtrate was adjusted to neutral and lyophilized to give 0.842g L-Cysteine-Mesna disulfide, with 72% yield.

¹H NMR (D₂O, 300 MHz) δ 3.05-3.14 (m, 3H), 3.27-3.35 (m, 3H), 3.97-4.01(dd, 1H, J=8.1 & 4.2 Hz). ¹³C NMR (D₂O, 75 MHz) δ 31.5, 39.0, 50.4,53.8, 174.4. HRMS Calcd. for C₅H₁₀NO₅S₃ Na₂ (M+Na): 305.9516; Found:305.9495.

Example 3 DL-Homocysteine-Mesna Disulfide

DL-Cysteine (0.42 g, 3.1 mmol) was dissolved in 25 mL de-ionized waterbubbled with argon. Excessive polystyrene p-sulfinate bound2-mercaptoethane sulfonic acid sodium salt (about 8.5 fold) was added.The reaction mixture was stirred under argon for approximately 4 daysuntil all starting material of DL-Homocysteine was consumed. The resinwas removed by filtration and was recycled to prepare more disulfides.The pH of filtrate was adjusted to neutral and lyophilized. Thelyophilized wet cake was then recrystallized from minimum requiredquantity of water to give 0.293 g (32%) DL-Homocysteine-Mesna disulfide

¹H NMR (D₂O, 300 MHz) δ 2.27-2.43 (m, 2H), 2.85-2.9 (m, 2H), 3.01-3.07(m, 2H), 3.26-3.31 (m, 2H), 4.11 (t, 1H, J=6.3 Hz,). ¹³C NMR (D₂O, 75MHz) δ 29.4, 31.7, 32.5, 50.4, 52.1, 172.4. HRMS Calcd. for C₆H₁₄NO₅S₃(M−Na+2H): 276.0034; Found: 276.0029.

Example 4 Glutathione-Mesna Disulfide

Glutathione (0.54 g, 1.76 mmol) was dissolved in 25 mL de-ionized waterbubbled with argon. Excessive polystyrene p-sulfinate bound2-mercaptoethane sulfonic acid sodium salt (about 15 fold) was added.The reaction mixture was stirred under argon for 4 approximately daysuntil all starting material of glutathione was consumed. The resin wasremoved by filtration and was recycled to prepare more disulfides. ThepH of filtrate was adjusted to neutral and lyophilized to give 486 mgGlutathione-Mesna disulfide, with 59% yield.

¹H NMR (D₂O, 300 MHz) δ 2.07-2.14 (m, 2H), 2.47-2.54 (m, 2H), 2.94-3.08(m, 3H), 3.25-3.32 (m, 3H), 3.66-3.71 (m, 1H), 3.75 (d, 2H, J=3.3 Hz),4.71 (m, 1H). ¹³C NMR (D₂O, 75 MHz) δ 26.6, 31.4, 31.9 and 32.0, 38.8,43.6, 50.6, 52.6 and 52.8, 54.3, 172.0, 174.9, 175.2, 176.5. HRMS Calcdfor C₁₂H₂₂N₃O₉S₃ (M−Na+2H): 448.0518; Found: 448.0497.

Example 5 Cysteinyl glycine-Mesna Disulfide

Cysteinyl glycine (226 mg, 1.27 mmol) was dissolved in 25 mL de-ionizedwater bubbled with argon. Excessive polystyrene p-sulfinate bound2-mercaptoethane sulfonic acid sodium salt (about 20.5 fold) was added.The reaction mixture was stirred under argon for approximately 3 daysuntil all starting material of cysteinyl glycine was consumed. The resinwas removed by filtration and was recycled to prepare more disulfides.The pH of the filtrate was adjusted to neutral and lyophilized to give302 mg cysteinyl glycine-Mesna disulfide, with 70% yield.

¹H NMR (D₂O, 300 MHz) δ 3.07-3.19 (m, 3H), 3.27-3.39 (m, 3H), 3.93-4.1(m, 2H), 4.41 (dd, 1H, J=8.1, 5.4 Hz). ¹³C NMR (D₂O, 75 MHz) δ 31.8,37.9, 43.7, 50.4, 52.4, 168.5, 176.2.

Example 6 γ-Glutamylcysteine-Mesna disulfide

γ-Glutamyl cysteine (200 mg, 0.8 mmol) was dissolved in 25 mL de-ionizedwater bubbled with argon. Excessive polystyrene p-sulfinate bound2-mercaptoethane sulfonic acid sodium salt (about 32 fold) was added.The reaction mixture was stirred under argon for approximately 3 daysuntil all starting material of γ-Glutamyl cysteine was consumed. Theresin was removed by filtration and was recycled to prepare moredisulfides. The pH of the filtrate was adjusted to neutral andlyophilized to give 316 mg γ-Glutamyl cysteine-Mesna disulfide, with 96%yield.

¹H NMR (D₂O, 300 MHz) δ 2.1-2.2 (m, 2H), 2.47-2.53 (m, 2H), 2.95-3.08(m, 3H), 3.22-3.3 (m, 3H), 3.76 (t, J=6.3 Hz, 1H), 4.47 (dd, J=9.0 & 4.2Hz, 1H). ¹³C NMR (D₂O, 75 MHz) δ 31.9, 39.8, 44.0, 46.4, 50.5, 54.3,54.8, 174.6, 177.0.

The present invention also includes methods of using the Formula Icompounds, and formulations that include the Formula I compounds.Potential uses include, but are not limited to reducing toxicity ofantineoplastic and other toxic pharmaceuticals; reducing the toxicity oftoxic industrial, agricultural or military chemicals; reducing toxicityof acute or chronic exposure to radiation; treatment or mitigation ofsymptoms of a number of diseases, including diabetic complications,inflammatory arthritis, inflammatory bowel disease, septic shock, ARDSand others.

Particular methods of use include administering an effective amount ofthe Formula I compound (or a formulation thereof) to a patient in needof treatment, or as prophylactic measures to patients in danger ofexposure to one of the stated conditions. An effective amount forpurposes of this application means that amount necessary to achieve thedesired result. Since the Formula I compounds are of extremely lowtoxicity, large amounts (>40 g) can be administered safely with littleor no adverse effects. Dosage may be on a single dose basis, or may becarried out on a regular schedule, depending upon the needs of thepatient.

All patents, publications, scientific articles, web sites, and the like,as well as other documents and materials referenced or mentioned hereinare indicative of the levels of skill of those skilled in the art towhich the invention pertains, and each such referenced document andmaterial is hereby incorporated by reference to the same extent as if ithad been incorporated by reference in its entirety individually or setforth herein in its entirety. Applicant reserves the right to physicallyincorporate into this specification any and all materials andinformation from any such patents, publications, scientific articles,web sites, electronically available information, and other referencedmaterials or documents.

The written description portion of this patent includes all claims.Furthermore, all claims, including all original claims as well as allclaims from any and all priority documents, are hereby incorporated byreference in their entirety into the written description portion of thespecification, and Applicant reserves the right to physicallyincorporate into the written description or any other portion of theapplication, any and all such claims. Thus, for example, under nocircumstances may the patent be interpreted as allegedly not providing awritten description for a claim on the assertion that the precisewording of the claim is not set forth in haec verba in the writtendescription portion of the patent.

The claims will be interpreted according to law. However, andnotwithstanding the alleged or perceived ease or difficulty ofinterpreting any claim or portion thereof, under no circumstances mayany adjustment or amendment of a claim or any portion thereof duringprosecution of the application or applications leading to this patent beinterpreted as having forfeited any right to any and all equivalentsthereof that do not form a part of the prior art.

All of the features disclosed in this specification may be combined inany combination. Thus, unless expressly stated otherwise, each featuredisclosed is only an example of a generic series of equivalent orsimilar features.

It is to be understood that while the invention has been described inconjunction with the detailed description thereof, the foregoingdescription is intended to illustrate and not limit the scope of theinvention, which is defined by the scope of the appended claims. Thus,from the foregoing, it will be appreciated that, although specificembodiments of the invention have been described herein for the purposeof illustration, various modifications may be made without deviatingfrom the spirit and scope of the invention. Other aspects, advantages,and modifications are within the scope of the following claims and thepresent invention is not limited except as by the appended claims.

The specific methods and compositions described herein arerepresentative of preferred embodiments and are exemplary and notintended as limitations on the scope of the invention. Other objects,aspects, and embodiments will occur to those skilled in the art uponconsideration of this specification, and are encompassed within thespirit of the invention as defined by the scope of the claims. It willbe readily apparent to one skilled in the art that varying substitutionsand modifications may be made to the invention disclosed herein withoutdeparting from the scope and spirit of the invention. The inventionillustratively described herein suitably may be practiced in the absenceof any element or elements, or limitation or limitations, which is notspecifically disclosed herein as essential. Thus, for example, in eachinstance herein, in embodiments or examples of the present invention,the terms “comprising”, “including”, “containing”, etc. are to be readexpansively and without limitation. The methods and processesillustratively described herein suitably may be practiced in differingorders of steps, and they are not necessarily restricted to the ordersof steps indicated herein or in the claims.

The terms and expressions that have been employed are used as terms ofdescription and not of limitation, and there is no intent in the use ofsuch terms and expressions to exclude any equivalent of the featuresshown and described or portions thereof, but it is recognized thatvarious modifications are possible within the scope of the invention asclaimed. Thus, it will be understood that although the present inventionhas been specifically disclosed by various embodiments and/or preferredembodiments and optional features, any and all modifications andvariations of the concepts herein disclosed that may be resorted to bythose skilled in the art are considered to be within the scope of thisinvention as defined by the appended claims.

The present invention has been described broadly and generically herein.Each of the narrower species and subgeneric groupings falling within thegeneric disclosure also form part of the invention. This includes thegeneric description of the invention with a proviso or negativelimitation removing any subject matter from the genus, regardless ofwhether or not the excised material is specifically recited herein.

It is also to be understood that as used herein and in the appendedclaims, the singular forms “a,” “an,” and “the” include plural referenceunless the context clearly dictates otherwise, the term “X and/or Y”means “X” or “Y” or both “X” and “Y”. The letter “s” following a noundesignates both the plural and singular forms of that noun. In addition,where features or aspects of the invention are described in terms ofMarkush groups, it is intended, and those skilled in the art willrecognize, that the invention embraces and is also thereby described interms of any individual member and any subgroup of members of theMarkush group, and Applicant reserves the right to revise theapplication or claims to refer specifically to any individual member orany subgroup of members of the Markush group.

Other embodiments are within the following claims. The patent may not beinterpreted to be limited to the specific examples or embodiments ormethods specifically and/or expressly disclosed herein. Under nocircumstances may the patent be interpreted to be limited by anystatement made by any Examiner or any other official or employee of thePatent and Trademark Office unless such statement is specifically andwithout qualification or reservation expressly adopted in a responsivewriting by Applicants.

1. A compound to reduce the toxicity of chemotherapeutic agents havingthe Formula I: X—S—S—R₁—R₂, wherein: R₁ is —(CH₂)₂—; —R₂ is SO₃^(− or C—PO(OH)) ₂; X is γ-Glutamylcysteine; andpharmaceutically-acceptable salts and prodrugs thereof.